A method for preparing a graphite-based boride ceramic modified Si-SiC ceramic coating material

Abstract

The present application relates to the technical field of graphite-based ceramic coating material, in particular to a preparation method of graphite-based boride ceramic modified Si-SiC ceramic coating material. The present application obtains single-phase entropy boride ceramic by ball-milling and mixing metal oxide powder of TiO2, ZrO and Ta2O5, B4C and C powder, and then vacuum heat treating twice, and then obtains graphite-based (Ti 1 / 3 Zr 1 / 3 Ta 1 / 3 )B2-Si-SiC ceramic coating material by mixing the entropy boride ceramic as modifier with Si and SiC and then carrying out discharge plasma sintering. The present application adopts boron / carbon thermal reduction method and discharge plasma sintering method to prepare a kind of entropy boride ceramic with excellent high-temperature oxidation resistance, the molecular formula of the entropy boride ceramic is (Ti 1 / 3 Zr 1 / 3 Ta 1 / 3 )B2, which has a hexagonal close-packed structure, and doping and modifying Si-SiC coating with the entropy boride ceramic can significantly improve the density and high-temperature oxidation resistance of Si-SiC coating, and has broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of graphite-based ceramic coating materials technology, specifically to a method for preparing graphite-based boride ceramic modified Si-SiC ceramic coating materials. Background Technology

[0002] Traditional ultra-high temperature ceramics, including borides such as ZrB2, HfB2, and TaB2, possess high melting points, good oxidation resistance, and excellent mechanical properties, making them widely used in aerospace, energy, and extreme manufacturing industries. However, due to the inherent brittleness of traditional ultra-high temperature ceramics under extreme environments, their mechanical properties and stability require improvement.

[0003] In ceramic materials, medium / high entropy ceramics significantly improve the overall performance of materials through mechanisms such as lattice distortion, hysteretic diffusion, cocktail effect, and enhanced thermodynamic stability. Therefore, medium / high entropy ceramics, as an emerging member of the multi-element ultra-high temperature ceramic family, have attracted the interest of researchers. In 2016, Gild et al. first prepared (Hf... 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 Seven types of high-entropy boride ceramics, including B2, generally exhibit superior hardness and oxidation resistance compared to single-component diborides manufactured using the same process. Ni et al. studied high-entropy carbide ceramics (Hf... 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 The ablation behavior of C in an oxyacetylene flame at 2000℃ was investigated, and it was found that the composite phase oxides generated during the ablation process provided effective oxygen barrier capabilities.

[0004] Current research on multi-component solid solution ultra-high temperature ceramics mainly focuses on high-entropy ceramics, whose excellent performance is attributed to their unique entropy effect and synergistic effects among multiple elements. However, due to the involvement of multiple elements and the significant differences in their physicochemical properties, the mechanism behind the superior performance of high-entropy ceramics is difficult to explain clearly. Therefore, some researchers have chosen medium-entropy ceramics with fewer elements. To investigate the influence of the types of components in multi-component ultra-high temperature ceramics on their performance, Zhang et al. studied C / C composite materials (Hf... 1 / 3 Zr 1 / 3 Ta 1 / 3The ablation performance of the C solid solution ceramic coating at 2100℃ was studied. The dense oxide film generated during the ablation process resulted in a low linear ablation rate (-0.61 μm / s). Huo et al. prepared medium-entropy (Ta,Zr,Ti)B2 ceramics using 10 vol.% cobalt and 20 vol.% SiC as additives and investigated their tribological properties under different loads. The oxide layer generated during the friction process effectively reduced the friction coefficient (0.459) under a high load of 10 N. However, the materials prepared in the above studies are not single-phase solid solution medium-entropy ceramics, and there is currently limited research on single-phase medium-entropy ceramics.

[0005] Carbon materials (graphite, carbon / carbon composites) are among the most promising materials for hot-end components in aerospace vehicles. However, they are easily oxidized above 450°C. SiC-based ceramic coatings exhibit excellent thermochemical and thermophysical compatibility with carbon materials, forming a protective SiO2-containing silicate glassy oxide layer, which effectively improves the oxidation resistance of the material. However, the SiC coating itself is brittle and easily cracks or peels off from the carbon substrate under high external loads. Furthermore, the SiO2 produced by oxidation easily evaporates at high temperatures, generating numerous pores and bubbles in the SiO2 oxide film, ultimately leading to the failure of the SiC-based composite coating. Currently, medium / high entropy ceramics have become candidate materials for novel ultra-high temperature protective coatings. The composite oxides with a wide melting point range formed by medium / high entropy ceramics at high temperatures, along with the introduction of entropy effects, make them suitable as basic components of ultra-high temperature protective coating materials, improving the oxidation resistance of carbon materials. Currently, there is limited research and application of medium / high entropy ceramic coatings or traditional coatings modified with medium / high entropy ceramics. Introducing medium entropy ceramics into Si-SiC coatings holds promise for developing a novel ultra-high temperature protective coating that can be applied in extreme environments such as aerospace. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing graphite-based boride ceramic modified Si-SiC ceramic coating materials, so as to solve the problem of poor high-temperature oxidation resistance of existing Si-SiC coatings.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a graphite-based boride ceramic modified Si-SiC ceramic coating material, comprising the following steps:

[0008] Preparation of S1, Boride Ceramic Powder

[0009] Take TiO2, ZrO2, Ta2O5, B4C, and C as raw material powders, mix them thoroughly, and then perform heat treatment to obtain boride ceramic powder. The boride ceramic powder is of medium entropy (TiO2). 1 / 3 Zr 1 / 3 Ta 1 / 3B2 ceramic powder is a single-phase solid solution with a close-packed hexagonal structure.

[0010] Preparation of S2, boride ceramic powder, Si and SiC mixed powder and pretreatment of graphite matrix

[0011] Take the boride ceramic powder obtained from S1, Si and SiC raw material powder, mix them thoroughly to obtain a mixed powder; take the graphite matrix, grind, polish, ultrasonically clean and dry to obtain a pretreated graphite matrix;

[0012] S3, Graphite-based (Ti 1 / 3 Zr 1 / 3 Ta 1 / 3 Preparation of B2-Si-SiC ceramic coating materials

[0013] The mixed powder obtained in S2 is coated onto the pretreated graphite matrix and then sintered by discharge plasma to obtain the graphite-based (Ti) matrix of this invention. 1 / 3 Zr 1 / 3 Ta 1 / 3 B2-Si-SiC ceramic coating material.

[0014] Furthermore, in S1, the particle size of each raw material powder is 1-3 μm, and the purity is ≥99.9%; the molar ratio of TiO2, ZrO2, Ta2O5, B4C and C is 1:1:0.5:1.65-3:3-8 respectively; wherein, the molar amount of B4C exceeds 10% of the molar amount of B4C required according to the stoichiometric ratio.

[0015] Further, in step S1, the raw material powders are ball-milled and thoroughly mixed, then dried and sieved to obtain the corresponding mixed powder. The resulting mixed powder is then pressed into blocks and subjected to a first heat treatment in a vacuum sintering furnace to obtain ceramic blocks. The obtained ceramic blocks are then pulverized, sieved, and subjected to a second heat treatment in a vacuum sintering furnace to obtain single-phase (Ti) ceramics. 1 / 3 Zr 1 / 3 Ta 1 / 3 B2 ceramic powder.

[0016] Furthermore, in both the primary and secondary heat treatments, the vacuum degree is less than 5 Pa; the temperature of the primary heat treatment is not lower than 1450℃, and the temperature of the secondary heat treatment is not lower than 2000℃.

[0017] Furthermore, in the primary and secondary heat treatments, the heating rate is 10℃ / min below 1000℃; 8℃ / min between 1000 and 1500℃; and 5℃ / min above 1500℃. The holding time is not less than 1 hour. After heat treatment, the temperature is reduced to 1000℃ at a rate of 10℃ / min, and then naturally cooled to room temperature with the furnace.

[0018] Furthermore, in S2, the mass ratio of the medium-entropy boride ceramic powder, Si, and SiC raw material powder is 5:4:16, wherein the particle size of the Si and SiC raw material powders is ≤200 mesh; the raw material powders are ball-milled and thoroughly mixed, then dried and sieved to obtain the corresponding mixed powder.

[0019] Furthermore, in S2, the graphite substrate is a graphite disc with a specification of Φ18mm×3mm; the graphite disc undergoes a pretreatment process of first polishing, water washing, second polishing, water washing, ultrasonic cleaning, and drying; the first polishing uses 200-mesh SiC sandpaper, and the second polishing uses 800-mesh SiC sandpaper.

[0020] Furthermore, in S3, during discharge plasma sintering, the vacuum degree is less than 5 Pa, the sintering temperature is not lower than 1900℃, and the sintering pressure is 40 MPa.

[0021] Furthermore, during the discharge plasma sintering, the heating rate is 100℃ / min below 1000℃; 50℃ / min between 1000 and 1500℃; and 30℃ / min above 1500℃. The holding time is not less than 10min. After sintering, the temperature is reduced to 1000℃ at a rate of 50℃ / min, and then cooled to room temperature with the furnace.

[0022] The beneficial effects of this invention are:

[0023] In this invention, entropy (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 B2 boride ceramics are single-phase solid solutions with a close-packed hexagonal structure, high purity, and dense structure. (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 The preparation method of B2-Si-Si ceramic coating is simple to operate, the coating is tightly bonded to the substrate, the coating surface is smooth, the composition is uniformly distributed, and the thickness is controllable. This invention effectively improves the high-temperature oxidation resistance of Si-SiC coating by introducing medium-entropy boride ceramics, and provides a new way to modify Si-SiC coating, which has broad application prospects. Attached Figure Description

[0024] Figure 1 This is Embodiment 1 of the present invention (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 X-ray diffraction pattern of B2 boride ceramic powder;

[0025] Figure 2 This is Embodiment 1 of the present invention (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3X-ray diffraction pattern of B2-Si-SiC coating;

[0026] Figure 3 This is Embodiment 1 of the present invention (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 Surface morphology photograph of B2-Si-SiC coating;

[0027] Figure 4 This is Embodiment 1 of the present invention (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 Cross-sectional morphology photographs of the B2-Si-SiC coating;

[0028] Figure 5 This is Embodiment 1 of the present invention (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 Oxidation curve of B2-Si-SiC coating after oxidation at 1500℃ for 40h;

[0029] Figure 6 This is Embodiment 1 of the present invention (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 Surface morphology of B2-Si-SiC coating after oxidation at 1500℃ for 40 h;

[0030] Figure 7 This is the X-ray diffraction pattern of the ceramic powder obtained in Comparative Example 1 of this invention;

[0031] Figure 8 This is an oxidation curve of the Si-SiC coating obtained in Comparative Example 2 of the present invention after oxidation at 1500℃ for 10 hours. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0033] Example 1

[0034] The raw material powders TiO2, ZrO2, Ta2O5, B4C, and C were calculated and weighed according to a molar ratio of 1:1:0.5:1.65:5, with the molar amount of B4C exceeding the required molar amount according to the stoichiometric ratio by 10%. All raw materials had a particle size of 1-3 μm and a purity ≥99.9%. Subsequently, the raw material powders, 3 mm diameter zirconia balls, and anhydrous ethanol were added to a ball mill jar at a mass ratio of 1:5:5. The ball milling time and speed were 12 h and 90 rpm, respectively. After milling, the grinding balls in the slurry were separated using a 30-mesh stainless steel sieve. The separated slurry was then placed in an 80℃ constant temperature drying oven and dried for 12 h. The dried powder was then sieved using a 200-mesh stainless steel sieve to obtain a uniformly mixed raw material powder.

[0035] The mixed powder was pressed into blocks and placed in a graphite crucible. A boron / carbothermic reduction reaction was carried out in a vacuum sintering furnace with a vacuum degree of less than 5 Pa. The temperature was raised to 1450℃ for heat treatment. The heating rate was 10℃ / min below 1000℃ and 8℃ / min between 1000℃ and 1450℃. After heating, the temperature was held for 2 hours and then lowered to 1000℃ at a rate of 10℃ / min. Finally, the temperature was cooled to room temperature with the furnace to obtain ceramic blocks.

[0036] The obtained ceramic blocks were crushed and ground in an agate mortar and passed through a 200-mesh sieve to obtain ceramic powder. The obtained ceramic powder was pressed into blocks, placed in a graphite crucible, and subjected to secondary heat treatment in a vacuum sintering furnace at 2000℃. The heating rate was 10℃ / min below 1000℃; 8℃ / min between 1000 and 1500℃; and 5℃ / min above 1500℃. After heating, the temperature was held for 2 hours, and then reduced to 1000℃ at a rate of 10℃ / min. Finally, the temperature was cooled to room temperature in the furnace. The obtained ceramic blocks were then crushed and ground in an agate mortar and passed through a 200-mesh sieve to obtain single-phase (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 The X-ray diffraction pattern of B2 ceramic powder (TZTB) was measured and compared with the X-ray diffraction pattern calculated by Materials Studio software. The results are as follows: Figure 1 As shown. By Figure 1 It can be concluded that the diffraction peak intensity and position of the experimental results are consistent with the calculated results, and no other impurity phases were detected, indicating that a single-phase medium-entropy boride ceramic with a close-packed hexagonal crystal structure was successfully synthesized.

[0037] Boride ceramic powder, Si powder, and SiC powder were weighed according to a mass ratio of 5:4:16, wherein the particle size of Si powder and SiC powder is ≤200 mesh. Then, each raw material powder, zirconia balls with a diameter of 3 mm, and anhydrous ethanol were added to a ball mill jar according to a mass ratio of 1:5:5. The ball milling time and speed were 12 h and 90 rpm, respectively. After ball milling, the grinding balls in the slurry were separated using a 30-mesh stainless steel sieve. The separated slurry was then placed in an 80℃ constant temperature drying oven and dried for 12 h. The dried powder was then sieved using a 200-mesh stainless steel sieve to obtain a mixed powder of boride ceramic powder, Si, and SiC.

[0038] The graphite substrate was pretreated. Graphite discs with a size of 18mm×3mm were used as the substrate. First, the graphite discs were manually polished on 200-grit SiC sandpaper for 2 minutes. The residual particles on the graphite surface were rinsed off with water. Then, the discs were polished on 800-grit SiC sandpaper for 2 minutes. After rinsing off the residual particles on the surface, they were ultrasonically cleaned at a frequency of 40kHz for 5 minutes to remove impurities. After that, they were placed in an 80℃ constant temperature drying oven to dry for 12 hours.

[0039] The mixed powder and the pretreated graphite substrate were then placed into a Φ20mm discharge plasma sintering mold, with clean carbon paper separating the powder and the mold. 1.5g of powder was weighed and wrapped around the graphite substrate in the center, and the powder surface was flattened after each step to ensure the uniformity of the coating. After the mold was installed, discharge plasma sintering was performed at a temperature of 1900℃, a holding time of 20min, and a sintering pressure of 40MPa.

[0040] The sintering temperature program is as follows: below 1000℃, the heating rate is 100℃ / min; 1000~1500℃, the heating rate is 50℃ / min; above 1500℃, the heating rate is 30℃ / min; during the cooling process, the temperature is reduced to 1000℃ at a rate of 50℃ / min, after which the program ends, and the furnace is cooled to room temperature. After removal, the carbon paper is removed by sanding, thus obtaining graphite-based (Ti) graphite. 1 / 3 Zr 1 / 3 Ta 1 / 3 The X-ray diffraction pattern of the B2-Si-SiC ceramic coating material is as follows: Figure 2 As shown. Its surface and cross-sectional morphology are respectively as follows. Figure 3 , Figure 4 As shown, the prepared coating material has a smooth surface, uniform composition distribution, and tight bonding with the substrate. The white phase is a medium-entropy boride ceramic, and the black phase is Si-SiC.

[0041] The obtained (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3After being oxidized at 1500℃ for 40 hours, the B2-Si-SiC ceramic coating material showed an increase in mass per unit area of ​​6.81 × 10⁻⁶. -3 g / cm 2 It has good antioxidant properties, and its oxidation curve is as follows: Figure 5 As shown.

[0042] like Figure 6 As shown, after being oxidized at 1500℃ for 40 hours, an oxide layer formed on the surface of the coating material. The black phase is SiO2, formed by the oxidation of Si and SiC; the light gray and dark gray phases are solid solutions formed by SiO2 and different precipitated metal elements (Ti, Zr, Ta), respectively; and the white phase is the metal oxides ZrO2 and TiTaO4. The SiO2 oxide layer protects the graphite matrix, and the metal oxides, pinned within the SiO2, enhance the high-temperature stability of the oxide layer. A few cracks exist in the oxide layer, but the overall structure is relatively intact.

[0043] Through the intermediate entropy (Ti) 1 / 3 Zr 1 / 3 Ta 1 / 3 B2 ceramic-modified Si-SiC coating significantly improves the density, high-temperature stability and high-temperature oxidation resistance of Si-SiC coating.

[0044] Comparative Example 1

[0045] The raw material powders TiO2, ZrO2, Ta2O5, B4C, and C were calculated and weighed according to a stoichiometric ratio of 1:1:0.5:1.545:5, with the excess molar amount of B4C accounted for by 3% of the stoichiometric molar amount. All powders had a particle size of 1-3 μm and a purity ≥99.9%. Subsequently, the raw material powders, 3 mm diameter zirconia balls, and anhydrous ethanol were added to a ball mill jar at a mass ratio of 1:5:5. The ball milling time and speed were 12 h and 90 rpm, respectively. After ball milling, the grinding balls in the slurry were separated using a 30-mesh stainless steel sieve. The separated slurry was then dried in an 80℃ constant temperature drying oven for 12 h. The dried powder was then sieved through a 200-mesh stainless steel sieve to obtain a uniformly mixed raw material powder.

[0046] The mixed powder was pressed into blocks and placed in a graphite crucible. A boron / carbon thermal reduction reaction was carried out in a vacuum sintering furnace with a vacuum degree of less than 5 Pa. The temperature was raised to 1450℃ for heat treatment, held for 2 hours, and then lowered to 1000℃ at a rate of 10℃ / min. Finally, the temperature was cooled to room temperature with the furnace.

[0047] The ceramic block was crushed and ground in an agate mortar and sieved through a 200-mesh sieve. The resulting ceramic powder was pressed into blocks, placed in a graphite crucible, and subjected to a second heat treatment at 2000°C using a vacuum sintering furnace to finally obtain ceramic powder. The heat treatment process was the same as in Example 1.

[0048] like Figure 7 As shown, the prepared ceramic powder exhibits diffraction peaks of TaC and TaB2, indicating that the powder is a mixture of these two substances. This suggests that during the sintering process, the B4C content was low, and a medium-entropy boride ceramic with a single-phase solid solution was not formed.

[0049] Comparative Example 2

[0050] Raw material powders Si and SiC were weighed at a mass ratio of 1:4. Both powders had a particle size of 1-3 μm, a purity ≥99.9%, and a particle size ≤200 mesh. Then, the raw material powders, 3 mm diameter zirconia balls, and anhydrous ethanol were added to a ball mill jar at a mass ratio of 1:5:5. The ball milling time and speed were 12 h and 90 rpm, respectively. After milling, the grinding balls in the slurry were separated using a 30-mesh stainless steel sieve. The separated slurry was then dried in an 80℃ constant temperature drying oven for 12 h. The dried powder was then sieved through a 200-mesh stainless steel sieve to obtain a uniformly mixed raw material powder.

[0051] The mixed powder is coated onto a pretreated graphite substrate (the graphite substrate pretreatment is the same as in Example 1), and high-temperature sintering is performed using the discharge plasma sintering method at a sintering temperature of 1900℃ (the sintering procedure is the same as in Example 1) to obtain a graphite-based Si-SiC ceramic coating material.

[0052] After the prepared Si-SiC ceramic coating material was oxidized at a constant temperature of 1500℃ for 10 hours, the mass per unit area decreased by 6.05 × 10⁻⁶. -2 g / cm 2 It has poor antioxidant properties, and its oxidation curve is as follows: Figure 8 As shown.

[0053] This invention is not limited to the preferred embodiments described above. Anyone can derive other forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for preparing a graphite-based boride ceramic-modified Si-SiC ceramic coating material, characterized in that, Includes the following steps: Preparation of S1, Boride Ceramic Powder Take TiO2, ZrO2, Ta2O5, B4C, and C as raw material powders, mix them thoroughly, and then perform heat treatment to obtain boride ceramic powder. The boride ceramic powder is of medium entropy (TiO2). 1 / 3 Zr 1 / 3 Ta 1 / 3 B2 ceramic powder is a single-phase solid solution with a close-packed hexagonal structure. The molar ratios of TiO2, ZrO2, Ta2O5, B4C, and C are 1:1:0.5:1.65~3:3~8, respectively; wherein the molar amount of B4C exceeds the required molar amount of B4C according to the stoichiometric ratio by at least 10%. The raw material powders are ball-milled and thoroughly mixed. After ball milling, the mixture is dried and sieved to obtain the corresponding mixed powder. The resulting mixed powder is then pressed into blocks and subjected to a first heat treatment in a vacuum sintering furnace to obtain ceramic blocks. The resulting ceramic blocks are then pulverized, sieved, and subjected to a second heat treatment in a vacuum sintering furnace to obtain single-phase (Ti) ceramics. 1 / 3 Zr 1 / 3 Ta 1 / 3 B2 ceramic powder; In both the primary and secondary heat treatments, the vacuum degree is less than 5 Pa; the temperature of the primary heat treatment is not lower than 1450℃, and the temperature of the secondary heat treatment is not lower than 2000℃. Preparation of S2, boride ceramic powder, Si and SiC mixed powder and pretreatment of graphite matrix Take the boride ceramic powder obtained from S1, Si and SiC raw material powder, mix them thoroughly to obtain a mixed powder; take the graphite matrix, grind, polish, ultrasonically clean and dry to obtain a pretreated graphite matrix; S3, graphite-based (Ti 1 / 3 Zr 1 / 3 Ta 1 / 3 Preparation of B2-Si-SiC ceramic coating materials The mixed powder obtained in S2 is coated onto the pretreated graphite matrix and then sintered by discharge plasma to obtain the graphite-based (Ti) matrix of this invention. 1 / 3 Zr 1 / 3 Ta 1 / 3 B2-Si-SiC ceramic coating material.

2. The method for preparing a graphite-based boride ceramic-modified Si-SiC ceramic coating material according to claim 1, characterized in that: In S1, the particle size of each raw material powder is 1~3μm and the purity is ≥99.9%.

3. The method for preparing a graphite-based boride ceramic-modified Si-SiC ceramic coating material according to claim 1, characterized in that: In the primary and secondary heat treatments, the heating rate is 10℃ / min below 1000℃; 8℃ / min between 1000 and 1500℃; and 5℃ / min above 1500℃. The holding time is not less than 1 hour. After heat treatment, the temperature is reduced to 1000℃ at a rate of 10℃ / min and then naturally cooled to room temperature with the furnace.

4. The method for preparing a graphite-based boride ceramic-modified Si-SiC ceramic coating material according to claim 1, characterized in that: In S2, the mass ratio of medium-entropy boride ceramic powder, Si, and SiC raw material powder is 5:4:16, wherein the particle size of Si and SiC raw material powder is ≤200 mesh; each raw material powder is ball-milled and thoroughly mixed, then dried and sieved to obtain the corresponding mixed powder.

5. The method for preparing a graphite-based boride ceramic-modified Si-SiC ceramic coating material according to claim 1, characterized in that: In S2, the graphite substrate is a graphite disc with a specification of Φ18mm×3mm. The graphite disc undergoes a pretreatment process of first polishing, water washing, second polishing, water washing, ultrasonic cleaning, and drying. The first polishing uses 200-mesh SiC sandpaper, and the second polishing uses 800-mesh SiC sandpaper.

6. The method for preparing a graphite-based boride ceramic-modified Si-SiC ceramic coating material according to claim 1, characterized in that: In S3, during discharge plasma sintering, the vacuum degree is less than 5 Pa, the sintering temperature is not lower than 1900℃, and the sintering pressure is 40 MPa.

7. The method for preparing a graphite-based boride ceramic-modified Si-SiC ceramic coating material according to claim 6, characterized in that: During the discharge plasma sintering process, the heating rate is 100℃ / min below 1000℃; 50℃ / min between 1000 and 1500℃; and 30℃ / min above 1500℃. The holding time is not less than 10 min. After sintering, the temperature is reduced to 1000℃ at a rate of 50℃ / min and then cooled to room temperature in the furnace.

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